Insitu FTIR investigation of the electrochemical microstructuring of n-Si(111)

Fourier transform infrared spectroscopy (FTIR) was used to investigate the hydrogenation of the silicon surface after the etch-back of an oxide layer and during photoelectrochemically induced roughening and smoothing treatments in an acidic fluoride containing solution. In case of the low ir-absorption of the Si-H stretching mode we applied multiple internal reflection techniques (MIR), whereas single internal reflection was used to monitor the formation of silicon oxide during light-assisted oxidation in this solution. The microtopography of the Si(lll)-surface is strongly influenced by the applied electrode potential under illumination and was inspected by use of field emission scanning electron microscopy (SEM) with a resolution of about 2 nm. The surface condition is changed between microscopically flat and rough (both SiH covered) or oxidized at higher anodic potentials (eletropolishing and photocurrent oscillations). Hydrogen-termination of the Si-surface was preserved even under low anodic currents in spite of the high etching rate in alkaline solutions.